1080p toggle in custom ROMs

I just read the XDA article for the Z5 Premium and how it switches automatically between 1080p and 4k resolution when it sees fit. I think this is an excellent idea for developers to implement into their ROMs. Why don't we have such a feature? Or even a simple toggle that we can select that would change the build.prop or something to switch between QHD and 1080p? Would it be too hard to included or something?

Just wondering, its a really neat feature.

Nick